1. Field of the Invention
The present invention relates generally to personal mobility vehicles (PMVs), and in particular to a PMV with a suspension providing control and tipping resistance over a wide variety of indoor and outdoor operating conditions.
2. Description of the Related Art
PMVs, which are also referred to as scooters, are becoming increasingly popular as mobility assistance devices for individuals with limited ambulatory function. They provide a number of advantages for users, some of whom might otherwise be forced to depend on others for assistance or use wheelchairs, walkers, canes, etc., all of which have significant mobility limitations. PMVs, on the other hand, are typically self-propelled and tend to liberate their riders, who can thereby enjoy relatively wide freedom of mobility, particularly in facilities that are compliant with the Americans with Disabilities Act (ADA) and other applicable codes, rules, etc.
Although such PMVs tend to function best on flat, level surfaces, their operators commonly encounter sloping (inclined, declined and side-to-side), convex, concave and otherwise uneven surface conditions. Moreover, their riders often require both indoor and outdoor mobility. For example, PMVs are frequently used away from home for access to areas, activities and events, which otherwise might be inaccessible to individuals with reduced ambulatory function. They are often transported in van-type vehicles and are therefore subject to space limitations while in transit. A dual-purpose indoor/outdoor PMV would therefore be preferable for ease of transportation.
Indoor operations often require relatively tight turning radii and compact vehicle designs in order to traverse corridors, pass through doorways and navigate other indoor conditions. Outdoor operations, on the other hand, can involve irregular natural ground surfaces, vehicle traction concerns and various other conditions. A dual-purpose (indoor and outdoor) PMV would be preferable, provided it could handle such varied operating conditions. Another PMV design criteria relates to disassembly into major components. Partially disassembled PMVs tend to be easier to store, transport and service. For example, separating the major components facilitates lifting and handling. Compact designs are often desirable for purposes of accessibility and for providing tighter turning radii. However, larger PMVs tend to be more stable. Therefore, PMV designs typically represent compromises involving such design criteria as size, stability, performance and maneuverability.
A common problem and concern with PMVs relates to stability and resistance to tipping. PMVs with larger wheel bases tend to be more stable, but less maneuverable. A partial solution is to provide a relatively short wheelbase from a steering front wheel to the main wheels for maneuverability, and to provide anti-tip trailing wheels, which are located behind the main wheels, for stability. Such trailing wheels tend to resist backwards tipping. For example, the Lo U.S. Pat. No. 6,896,084 shows a wheeled vehicle with a detachable rear frame including anti-tip wheels. Degonda et al. (U.S. Pat. No. 5,964,473) show trailing wheels mounted on a wheelchair.
Another PMV design issue relates to weight distribution. Five-wheel PMVs have steering front wheels, main wheels (at least one of which is driven) and anti-tip trailing wheels. Ideally most of the combined weight of the vehicle and the rider is on the main wheels for traction. However, the steering front wheel must also support a portion of the total load for control purposes. The proportional weight distribution, particularly on the main wheels, justly should remain relatively constant with riders of different sizes for maintaining traction and control.
Heretofore there has not been available a PMV with an anti-tip suspension subframe with the advantages and features of the present invention.